msem-instigator

Whenever you untap a nonland permanent, put a winding counter on Barton's Pocketwatch.
{T}: Look at the top card of your library. You may put it into your graveyard. Then if Barton's Pocketwatch has twelve or more winding counters on it, exile it and take an extra turn after this one.

Flash
Once each turn, you may cast a spell without paying its mana cost. If you do, at the beginning of your next upkeep, you lose the game unless you pay that spell's mana cost.

Lifelink
When Bastion Chaplain enters, create two Function tokens with “Lifelink.” (They're enchantments. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Create two 1/1 white Avatar enchantment creature tokens with prowess.
Conjure a card named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)

Flying, first strike, vigilance, lifelink
When Bastion Valkyrie dies, create three Function tokens with “Choose a creature targeted by this spell. It gains flying, first strike, vigilance, and lifelink until end of turn.” (They're enchantments. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

When Bastion Warden enters, exile target creature an opponent control until target enchantment you control leaves the battlefield.

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast enchantment spells or to activate an ability of an enchantment.
When Bastion, Node of the Free is destroyed, return it to its owner's hand.

At the beginning of your upkeep, you may discard a card. If you do or if you control a creature with power 4 or greater, draw a card.

Deploy 2 (As this enters, you may tap any number of other creatures you control with total power 2 or more.)
When Battlefield Preserver enters deployed, exile target nonland permanent until Battlefield Preserver leaves the battlefield.

Beachhead Partisan has first strike as long as it's attacking.
When Beachhead Partisan enters, it deals X damage to any target, where X is the number of tapped creatures you control.

Whenever you cast an instant or sorcery spell, each opponent loses 1 life and Beast of Pestilence gets +1/+1 until end of turn.

Menace
When Beatrice enters, target opponent reveals their hand. Exile a nonland card from it. During any turn that player lost life, you may cast that card and mana of any type can be spent to cast that spell.

When Benthic Alchemist enters, draw a card, then discard a card, then mill a card.
Whenever you cast an instant or sorcery spell, create a 1/1 colorless Elemental creature token. It gains haste until end of turn.

When Bio-Sequencer enters, conjure a card named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)
{1}, {T}, Sacrifice Bio-Sequencer: Add one mana of any color.

Exchange control of two target permanents that share a permanent type.
Lifecycle {3} ({3}, Discard this card: Create two tapped 1/1 colorless Elemental creature tokens.)

Target opponent reveals their hand. You choose an instant or sorcery card from it or a card from their graveyard. Exile that card.

When Blacksite Moderator enters, you may pay 2 life or sacrifice a permanent. If you do, draw a card.

Lifelink
{T}, Pay 4 life or sacrifice another permanent: Draw a card.

When Blackwall Ramparts enters, exile up to two target nonland permanents you don't control with total mana value 8 or less until Blackwall Ramparts leaves the battlefield.
Whenever you draw a card, you gain 1 life.

Double strike
Attain {3}{R} ({3}{R}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

Haste
When Blighted Dullahan dies, you draw a card and you lose 1 life.

Breach (Whenever this deals combat damage to a player, you may have it become an Aura Curse until your next turn. Attach it to that player.)
At the beginning of your end step, each cursed opponent loses 2 life unless they discard a card.

When Bloodpact Collector enters, destroy target creature an opponent controls that was dealt damage this turn or has a -1/-1 counter on it.

Flying, prowess
When Bound Watcher enters, conjure a card named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)

Trample
{1}{G}: Brackish Kelpie gets +2/+2 until end of turn. Activate only once each turn.